Basic knowledge of the hottest industrial cleaning

Basic knowledge of industrial cleaning

I. classification of cleaning methods:

1. Physical cleaning method 2 Chemical cleaning method 3 Electronic cleaning method (electronic descaling and anti scaling) 4. Electrostatic cleaning method (electrostatic descaling and anti scaling)

(1) physical cleaning method is a cleaning method that applies external force to remove all kinds of pollutants with the help of hand tools and machinery without changing the components of pollutants. That is, the method of not changing the original chemical molecular components? Br>

① mechanical cleaning method: cleaner and scraper cleaning method, drill pipe cleaning method, shot blasting cleaning method

② hydraulic cleaning method: low pressure hydraulic cleaning (the pressure of low pressure cleaning is kPa, about kgf/cm2, equal to 0..7mpa)

③ high pressure hydraulic cleaning: the pressure of high pressure cleaning is 4900 kPa, about 50 kgf/cm2, equal to 5MPa. This method is also called high-pressure water jet method and high-pressure cleaning machine

(2) the principle of anti scaling and descaling of electronic cleaning method is to use high-frequency electric field to change the molecular structure of water to prevent and remove scaling. When water passes through the high-frequency electric field, its molecular physical structure changes. The original associating chain macromolecule breaks into a single water molecule. The positive and negative ions of salts in the water are surrounded by a single water molecule, so the movement speed is reduced, the number of effective collisions is reduced, and the electrostatic attraction is reduced. It is impossible to structure on the heated wall surface, so as to achieve the purpose of scale prevention. At the same time, due to the increase of the dipole moment of water molecules, the attraction ability between water molecules and salt positive and negative ions (scale molecules) increases, which makes the scale on the heating surface or pipe wall become soft and easy to fall off, resulting in the effect of descaling.

(3) electrostatic descaling and descaling, like electronic descaling, also achieve the purpose of descaling and descaling by changing the state of water molecules. But the latter is the use of electrostatic fields, rather than the role of electrons. The mechanism is that water molecules have polarity (also known as dipoles). When water dipoles pass through the electrostatic field, it is considered that the following adjustments should be made in view of the above situation: each water dipole will be continuously arranged in order of positive and negative. For example, if the water contains dissolved salts, its positive and negative ions will be surrounded by water dipoles and arranged in the water dipoles in positive and negative order. They cannot move by themselves, so they cannot be close to the pipe (vessel) wall, and then deposit on the pipe (vessel) wall to form scale. At the same time, the oxygen released from the water can produce a very thin oxide layer on the pipe wall, so when using it, 1 be careful with the wings, which can prevent the supply guarantee of the pipe (device): the finished product stock wall of conventional products is corroded

(4) chemical cleaning method: use chemical agents to remove the surface pollution or the covering layer (such as the scale layer) by chemical reaction with it, such as acid pickling and alkali washing of the scale layer. In order to prevent the substrate from corrosion during chemical cleaning or control the corrosion rate within the allowable range, an appropriate amount of corrosion inhibitor and additives for activation, penetration and wetting are usually added to the chemical cleaning solution. Methods: immersion method, circulation method and cleaning method in operation are also called non-stop chemical cleaning method

II. Characteristics of main metal materials

(1) general term of alloy steel resistant to acid, alkali, salt and other corrosion. Mainly chromium containing alloy steel. After chromium is added, the steel has high corrosion resistance. In addition, adding nickel, molybdenum, titanium, manganese, nitrogen and other elements to chromium steel can improve its corrosion resistance and process performance. The chromium content in stainless steel is generally not less than 12%. There are two common categories: chromium stainless steel (containing 12% chromium or more) and nickel chromium stainless steel (containing 12% chromium and 8% nickel)

(2) cast iron is an iron carbon alloy containing more than 2% carbon, and contains manganese, silicon and a small amount of phosphorus and sulfur. It is brittle and hard without ductility

(3) carbon steel, also known as carbon steel, has a carbon content of 0%, According to the carbon content, it can be divided into low carbon steel, medium carbon steel or high carbon steel

(4) copper alloy. Copper is a non-ferrous metal with good ductility. It is soft, conductive and thermally conductive. Copper and other metals can form many alloys with good properties, such as bronze (containing 80% copper, static arc height or arc height deviation under specified load mm, tin 15%, zinc 5%), brass (containing copper%, zinc%), easy to process, and many mechanical parts are made of brass

(5) aluminum alloy. Aluminum is a light metal with good ductility. Aluminum is easy to be oxidized in the air, and a dense oxide film is formed on the surface, which can protect itself. Aluminum and many metals can form alloys with small specific gravity and high strength, which are widely used in various industries

III. corrosion inhibitor refers to the introduction of corrosivity. Adding a small amount of a substance can greatly reduce the corrosion rate of metal. This substance is called corrosion inhibitor. This method of protecting metals is called inhibitor protection method

classification of corrosion inhibitors:

the mechanism of action is divided into anode, cathode and mixed type. The characteristics of protective film are divided into oxidation type, adsorption type and precipitation type. Other classifications: ① organic and inorganic corrosion inhibitors ② liquid phase, gas phase and solid phase corrosion inhibitors ③ steel, copper and aluminum corrosion inhibitors ④ acidic, alkaline and neutral corrosion inhibitors. (end)